This invention relates to a ball check valve preferred for use in devices related to sewage treatment.
The configuration of a conventional general ball check valve used, for example, in devices related to sewage treatment is shown in FIGS. 1 and 2. As shown in these drawings, a ball 3 is movably housed in a ball chamber 2 provided inside a valve casing 1. A cover 4 is attached watertight to the valve casing 1 by bolts 6 via an O-ring 5. The valve casing 1 is provided with an inflow port 7 and a discharge port 8, which are open to the outside. Inside the valve casing 1, a valve seat surface 9 and a ball guide portion 10 are formed. The ball guide portion 10 is formed along an opening portion 12 which is provided in a peripheral wall demarcating the ball chamber 2 so as to be open to a discharge-side channel 11 leading to the discharge port 8. A fluid flows into the valve casing 1 from the direction of an arrow I, and is discharged to the outside in the direction of an arrow O.
When a pump is operated to exert pressure on the inflow port 7, the ball 3 departs from the valve seat surface 9, and moves in the ball chamber 2 along the ball guide portion 10 in the direction of an arrow m. When the pump stops, the ball 3 falls to the valve seat surface 9 by its own weight to prevent a back flow.
With the foregoing conventional ball check valve, however, when the ball 3 moves along the ball guide portion 10, a part of the ball 3 is jammed in the discharge-side channel 11, as shown in FIG. 2. As a result, the area of a channel from the ball chamber 2 to the discharge-side channel 11 decreases to increase the fluid resistance. On the other hand, the ball check valve may be turned 90 degrees, and used in a horizontal posture, with the cover 4 facing upward. In this case, the ball 3 undergoes the force of the fluid, and can freely rotate in directions parallel to, and perpendicular to, the flow of the fluid. Thus, when the ball 3 rests on the valve seat surface 9, the ball 3 easily rotates on the valve seat surface 9 in the circumferential direction of the valve seat surface 9, resulting in poor adhesion of the ball 3 to the valve seat surface 9.
With the above-described conventional ball check valve, moreover, the valve casing 1 is either produced, for example, by integral molding of resin, or has its inner peripheral surface coated with resin, in consideration of corrosion resistance, etc. To hold the ball 3, which is inserted into the ball chamber 2, so as to be inescapable, the cover 4 constituted separately from the valve casing 1 is provided. Furthermore, the ball 3 is generally constituted by integrally covering the surface of a spherical, metallic core material 15 with an elastic body 16.
However, with the above conventional ball check valve, the valve seat surface 9 is formed inside the valve casing 1, so that the internal diameter of the inflow port 7 and the discharge port 8 cannot be made greater than the external diameter of the ball 3. If the opening areas of the discharge-side channel 11 and the opening portion 12 open to the discharge-side channel 11 are made larger than that of the discharge port 8, release of the mold at the time of molding poses a problem, and is considerably difficult.
Hence, certain limitations are imposed on the opening areas of the discharge-side channel 11 and the opening portion 12 open to the discharge-side channel 11. Besides, if the ball 3 is positioned at the opening portion 12, the ball 3 clogs a part of the opening portion 12, further decreasing the opening area. Thus, clogging with foreign objects tends to occur, and the fluid resistance increases. In addition, the valve seat surface 9 tends to wear, compared with the other portions, because of collision with the ball 3. If such wear occurs in the valve seat surface 9, replacement of the entire valve casing 1 is necessary, and it is uneconomical.
The elastic body 16 covering the surface of the ball 3 may peel, and the metallic core material 15 may be exposed to the outside. When this core material 15 contacts water, the core material 15 is selectively susceptible to corrosion, since the metal is generally electrochemically more ionizable than the surrounding resin. The use of a metal resistant to corrosion, for the purpose of preventing corrosion, leads to a high cost for the ball 3.
The present invention has been accomplished in light of the above problems. An object of the invention is to provide a ball check valve in which the area of a channel leading from a ball chamber to a discharge-side channel can be increased, and the adhesion of a ball to a valve seat surface is satisfactory even when the ball check valve is used in a horizontal posture.
Another object of the present invention is to provide a ball check valve in which an inner channel in a valve casing can be widened regardless of the size of the ball housed in the ball chamber, and even if an elastic body covering the surface of the ball peels, selective corrosion of a core material does not occur.
The ball check valve of the present invention is a ball check valve having a ball movably housed in a ball chamber provided inside a valve casing, characterized in that two or more rail-like ridges protruding toward the interior of the ball chamber to guide the ball are provided on a peripheral wall demarcating the ball chamber.
According to this feature, when the ball moves inside the ball chamber, the ball is guided by the rail-like ridges and situated more inwardly inside the ball chamber, and the area of a channel is correspondingly enlarged upwardly and downwardly of the ball. When the ball check valve is used in a horizontal posture, moreover, the free rotation of the ball in a direction perpendicular to the flow of a fluid is inhibited by the rail-like ridges, whereby the ball is prevented from rotating on the valve seat surface in a circumferential direction of the valve seat surface. Thus, the adhesion of the ball to the valve seat surface is improved.
The ball check valve is also characterized in that the rail-like ridges are disposed such that when the ball housed in the ball chamber contacts the peripheral wall of the ball chamber and the rail-like ridges, the center of gravity of the ball is positioned inwardly of the rail-like ridges.
According to this feature, even if the ball moves while deviating to one direction, the position of the ball is automatically corrected by a force acting on the ball to the normal position at which the ball is guided by the rail-like ridges. Since the position of the ball is so stabilized, the movement of the ball is smoothed.
The ball check valve of the present invention is also a ball check valve having a ball movably housed in a ball chamber provided inside a valve casing, characterized in that valve seats constituted separately from the valve casing are mounted, respectively, on an inflow side and a discharge side of the valve casing.
According to this feature, the valve seats mounted, respectively, on the inflow side and the discharge side of the valve casing form an inlet port and a discharge port having an internal diameter smaller than the external diameter of the ball housed inside the valve casing. Furthermore, the inner channel inside the valve casing can be widened in comparison with the internal diameter of the inflow port and the discharge port formed by the valve seats.
The ball check valve of the present invention is also a ball check valve having a ball movably housed in a ball chamber provided inside a valve casing, characterized in that the ball comprises a resinous core material having a surface coated with an elastic body.
According to this feature, even if the elastic body on the surface of the ball peels to bring the resinous core material into contact with water, the core material is prevented from selectively corroding, because the electrochemical stability of the core material is comparable to that of the surrounding resin. Furthermore, the ball can be produced for a low cost.